TECHNICAL FIELD
The present invention relates to a system and method for controlling data access in a computer network.
In recent years, there has been explosive growth in the Internet, and in particular of the WorldWide Web (WWW), which is one of the facilities provided via the Internet. The WWW comprises many pages or files of information, distributed across many different servers. Each page is identified by a Universal Resource Locator (URL). Each URL denotes both a server machine, and a particular file or page on that machine. There may be many pages or URLs resident on a single server.
To utilise the WWW, a user runs a computer program called a Web browser on a client computer system such as a personal computer. Examples of widely available Web browsers include the "WebExplorer" Web browser provided by International Business Machines Corporation in the OS/2 Operating System software, or the "Navigator" Web browser available from Netscape Communications Corporation. The user interacts with the Web browser to select a particular URL. The interaction causes the browser to send a request for the page or file identified in selected URL to the server identified in the selected URL. Typically, the server responds to the request by retrieving the requested page, and transmitting the data for that page back to the requesting client. The client-server interaction is usually performed in accordance with a protocol called the hypertext transfer protocol ("http"). The page received by the client is then displayed to the user on a display screen of the client. The client may also cause the server to launch an application, for example to search for WWW pages relating to particular topics.
WWW pages are typically formatted in accordance with a computer programming language known as hypertext mark-up language ("htm1"). Thus a typically WWW page includes text together with embedded formatting commands, referred to as tags, that can be employed to control for example font style, font size, lay-out etc. The Web browser parses the HTML script in order to display the text in accordance with the specified format. In addition, an html page also contain a reference, in terms of another URL, to a portion of multimedia data such as an image, video segment, or audio file. The Web Browser responds to such a reference by retrieving and displaying or playing the multimedia data. Alternatively, the multimedia data may reside on its own WWW page, without surrounding html text.
Most WWW pages also contain one or more references to other WWW pages, which need not reside on the same server as the original page. Such references may be activated by the user selecting particular locations on the screen, typically by clicking a mouse control button. These references or locations are known as hyperlinks, and are typically flagged by the Web browser in a particular manner. For example, any text associated with a hyperlink may be displayed in a different colour. If a user selects the hyperlinked text, then the referenced page is retrieved and replaces the currently displayed page.
Further information about html and the WWW can be found in "World Wide Web and HTML" by Douglas McArthur, p18-26 in Dr Dobbs Journal, December 1994, and in "The HTML SourceBook" by Ian Graham, John Wiley, New York, 1995.
Many organisations, particularly although not exclusively those in the entertainment industry, are now seeking to generate revenue from the Internet by granting users access to WWW pages and files, particularly those containing multimedia data, subject to an access charge to the user. Such electronic commerce has been inhibited because of difficulty in providing a secure method of charging and billing for transactions over the Internet. Conventional solutions to this problem have tended to involve credit card payments and the like. Such access control methods are however uneconomical in terms of data processing to be applicable to low cost transactions over the Internet.